I was horrified to see that the “Chatzum” malware sailed through Avast’s defences undetected and installed itself on my computer. Beware everyone - this is a helluva difficult bit of rogue software to remove.
Why hasn’t Avast devised some form of protection against this? It really is pernicious.
no security programs have 100% detection…
and as i understand Chatzum is not a infection…but some browser/toolbar crap…may be classed as PUP
Run AdwCleaner first… then do a quick scan with Malwarebytes, and click the "remove selected " button to quarantine anything found
(make sure Malwarebytes is updated before you run it)
you find them here http://forum.avast.com/index.php?topic=53253.0
you may post the scan logs here
if you still have problems… see in the same guide how to run and attach a OTL log
then one of the malware removers will remove it fore you 
Seriously this chatzum stuff is nasty, its not just a browser thing. It attempts to hack facebook and it is now like spaghetti all over the computer, all through registry. It needs stronger action. Also malwarebytes have also not detected it.
as i said above continue wit OTL if you still have problems
Its not a rogue…its adware…its not nasty and not serious infection…so keep calm
agree with true indian… not a dangerous stuff…
Also you must install WOT for all your browsers you use to avoid going to such notorious sites:
www.mywot.com/